Application of compound material alleviates saline and alkaline stress in cotton leaves through regulation of the transcriptome

Abstract

Background: Soil salinization and alkalinization are the main factors that affect the agricultural productivity. Evaluating the persistence of the compound material applied in field soils is an important part of the regulation of the responses of cotton to saline and alkaline stresses.

Result: To determine the molecular effects of compound material on the cotton's responses to saline stress and alkaline stress, cotton was planted in the salinized soil (NaCl 8 g kg^{- 1}) and alkalized soil (Na₂CO₃ 8 g kg^{- 1}) after application of the compound material, and ion content, physiological characteristics, and transcription of new cotton leaves at flowering and boll-forming stage were analyzed. The results showed that compared with saline stress, alkaline stress increased the contents of Na⁺, K⁺, SOD, and MDA in leaves. The application of the compound material reduced the content of Na⁺ but increased the K⁺/Na⁺ ratio, the activities of SOD, POD, and CAT, and REC. Transcriptome analysis revealed that after the application of the compound material, the Na⁺/H⁺ exchanger gene in cotton leaves was down-regulated, while the K⁺ transporter, K⁺ channel, and POD genes were up-regulated. Besides, the down-regulation of genes related to lignin synthesis in phenylalanine biosynthesis pathway had a close relationship with the ion content and physiological characteristics in leaves. The quantitative analysis with PCR proved the reliability of the results of RNA sequencing.

Conclusion: These findings suggest that the compound material alleviated saline stress and alkaline stress on cotton leaves by regulating candidate genes in key biological pathways, which improves our understanding of the molecular mechanism of the compound material regulating the responses of cotton to saline stress and alkaline stress.

Keywords: Alkalinization; Antioxidant; Compound material; K+/Na+ ratio; Lignin biosynthesis; Salinization.

Fig. 1

Effect of the application of compound material on K⁺ and Na⁺ contents and K⁺/Na⁺ ratio (a), antioxidative enzymes activity, and MDA and REC contents (b) in leaves

Fig. 2

Transcriptome analysis of cotton leaves in response to the application of compound material regulating saline stress and alkaline stress. Numbers of DEGs identified in cotton leaves (a). Venn diagram of DEGs (b)

Fig. 3

GO enrichment analysis of DEGs. The top 10 enriched GO terms in NaCl treatments (CK-Y and P-Y treatments). The top 10 enriched GO terms in Na₂CO₃ treatments (CK-J and P-J treatments) (a); The top 10 enriched GO terms in the controls (CK-J and CK-Y treatments) (b); The top 10 enriched GO terms in compound material treatments (P-J and P-Y treatments) (c); BP, CC, and MF represent biological process, cellular component, and molecular function, respectively (d). The asterisks represent the significant level of 0.05

Fig. 4

Correlation analysis between transcription genes of K⁺, Na⁺ (a) and physiological characteristics (b)

Fig. 5

Representation of genes related to phenylpropanoid biosynthesis pathway (https://www.kegg.jp/dbget-bin/www_bget?map00940). The red frames represent up-regulated DEGs, the green frames represent down-regulated DEGs. Pathway in NaCl treatments (CK-Y and P-Y treatments (a); Pathway in Na₂CO₃ treatments (CK-J and P-J treatments) (b); Pathway in control treatments (CK-J and CK-Y treatments) (c); Pathway in compound material treatments (P-J and P-Y treatments) (d) (State: We obtained the appropriate copyright permission to modify the phenylpropanoid biosynthesis pathway)

Fig. 6

Proposed model for the function of compound material in regulating saline stress (a) and alkaline stress (b) of cotton leaves. The up-pointing red arrows mean that the candidate genes are up-regulated; the down-pointing blue arrows mean that the candidate genes are down-regulated